Liposomes are vesicular systems composed of a lipid bilayer, used like cell models in basic research. Liposomes have gained extensive attention as carriers for a wide range of drugs due being both nontoxic and biodegradable because they are composed of naturally occurring substances existing in biological membranes. Biologically active materials encapsulated within liposomes are protected to varying extent from immediate dilution or degradation, which makes them good drug delivery systems for the transport of drugs or other bioactive compounds to organs affected. The unique ability of liposomes to entrap drugs both in an aqueous and a lipid phase make such delivery systems attractive for hydrophilic and hydrophobic drugs (Chrai S. et al., 2002; Hong M. et al., 2001). Liposome technology has broad potential applications, from cosmetics to delivery of drugs in cancer chemotherapy, anti-inflammatory therapy, cancer imaging agents and gene therapy. However, the delivery of therapeutical compounds is restricted by the low selectivity of therapeutic drugs, resulting in by harmful toxic effects on normal organs and tissues (Immordino M. et al., 2006). The delivery of the compounds to specific cell types, for example, cancer cells or cells of specific tissues and specific organs can be realized by using receptors associated with specific cell types. Unlike many other methods, receptor mediated endocytotic activity can be used successfully both in vivo and in vitro (Varghese B. et al., 2007). Receptor mediated endocytosis involves the movement of ligands bound to membrane receptors into the interior of an area bounded by the membrane through invagination of the membrane. Thus, for the purpose of selectively making a drug delivery to specific tissues and cells, the surface of the liposomes can often be modified with specific ligands (Gabizon. A. et al., 1999; Turk M. et al., 2002). Particular receptors are overexpressed in certain cancerous cells, including the high affinity folic acid receptor. The high affinity folate receptor is a tumour marker that is overexpressed in a variety of neoplastic tissues, including breast, ovarian, cervical, colorectal, renal, and nasoparyngeal tumours, but is expressed to a very limited extent in normal tissues (Turk H. et al., 2002; Wu J. et al., 2006). The folic acid receptor is also expressed in activated macrophages that persist in sites of inflammation, in inflammatory diseases such as Rheumatoid Arthritis (RA) (Chen W. et al., 2005; Paulos C. et al., 2004). The use of folic acid as a basis to obtain conjugates to transport exogenous compounds across cell membranes can a targeted delivery approach to the treatment and diagnosis of disease (ex., cancer and RA) and can provide a reduction in the required dose of therapeutic compounds. Furthermore, therapeutic bioavailability, pharmacodynamics, and pharmacokinetic parameters can be modulated through the use of bioconjugates, including folate bioconjugates. The use of folate ligands as a targeting device provides a number of important advantages over other targeting ligands. They are inexpensive, nontoxic, nonimmunogenic, easy to conjugate to carriers, retain high binding affinity, and are stable in storage and in circulation. (Shmeeda H. et al., 2006).
The use of folate conjugates to enhance transmembrane transport of exogenous molecules has been reported by Low et al., (EUA Pat. N° s 5.416.016, 5.108.921 and WO 90/12096). Manoharan et al. (International PCT publication N° WO 99/66063) describe certain folate conjugates and its synthesis method. The US 2006062842 patent (Gabizon et al., 2006) described a method of administering a compound encapsulated in liposomes as therapeutic to multi-drug resistant cancer cells. This method includes also the folic acid covalently bound to a hydrophobic polymer incorporated in liposomes. The same author (Gabizon at al, 2010) WO 2010143193, also describe the use of targeted liposomes by folic acid to enacapsulation of amino-biphosphate, to several diseases treatment. Sideratou al (2008), described in WO 2008010000 patent, modification of dendritic polymers with known groups, such as folic acid, with subsequent encapsulation in liposome bilayers, so-called preparing dendrionized liposomes. Dongkai et al. (2010), reported in CN 101684177 Patent the synthesis and use of folic acid conjugates linked to polyethylene glycol polycyanoacrylate (FA-PEG-PHDCA) due to excellent activity of the polymer and targeting property to cancer cells via folic acid, being the polymer applied to modify several vesicular systems such as liposomes. Although these studies reporting the use of folic acid as specific ligand to targeting, all formulations requires a prior binding of a polymer not specific to liposomal membranes. In the present invention, which describe peptide sequences with capacity of fixing in the liposomal membranes has the advantage of such formulations is not necessary to modification of liposomes with lipopolymers. The use of peptides to liposomes bonding have been explored based the so-called. “cell penetrating peptides”. These peptides are capable of crossing cellular membranes in vitro and in vivo with high efficiency (Deshayes S. at al., 2005). Among them there are peptides derived from protein transduction domains, which are able to across biological membranes without transporter or receptor, and delivery peptides or molecules in intracellular compartments. Examples of such peptides include a Penetratin, TAT, Transportan and VP22 (Magzoub M. et al., 2001). There are also a number of amphipathic peptides which combine one hydrophobic domain with a hydrophilic domain. Among these ones it's possible to enumerate MAP, KALA, ppTG20, Trimer, P1, MPG, and Pep-1 (Morris, M. at al., 2008). Other peptides are further described as penetration capability due various characteristics. Thus, peptides with positive charge are used for translocation processes (Deshayes, S. et al., 2005). Despite the unique characteristics of these peptides identified above for binding to liposomes, have not been described as conjugated to specific ligands, which largely limits its use.
The present invention relates to peptide sequences which due to their hydrophobic sequence are capable of strong penetration/inclusion into liposomes. After a folic acid binding or antibody of folic acid receptor at the N-terminus, allows these liposomes possess the capability of targeting specific cells expressing the folic acid receptor. This enables the specific release of therapeutic agents and/or imaging agents that are inside the liposome, either hydrophobic or hydrophilic. The therapeutic agents may be either pharmaceutical compounds (active agents) or siRNA. These pharmaceutical formulations are capable of being administered either topically or by intravenous administration.